1. Field of the Invention
The invention generally relates to biochemical/microbiological testing methodologies. More particularly, the invention relates to antifungal screening tests.
2. Description of the Relevant Art
Nosocomial (hospital acquired) infections are the fourth leading cause of death in the U.S. with 2 million cases and more than $5 billion in added medical cost per annum. A large number of these infections are fungal infections, and are often associated with implantable devices, intravascular and urinary catheters, orthopedic implants, and intrauterine contraceptive devices, which is an $180b per year industry. Fungal infections are much more lethal than bacterial infections as seen by mortality rates −50% for candidiasis, 90% for aspergillosis, and 100% for zygomycosis. For example, in pediatric patients, candidiasis (the most common fungal infection) is associated with a 10.0% increase in mortality, a mean 21.1-day increase in length of stay, and a mean increase in total per-patient hospital charges of $92,266. Similarly, in adult patients candidiasis is associated with a 14.5% increase in mortality, a mean 10.1-day increase in length of stay, and a mean increase in hospital charges of $39,331. Overall, these numbers suggest that despite having a market of $3.1b per year, which is ˜10% of all anti-infectives, currently used antifungals are still ineffective. There are no new effective drugs in sight, and the antifungal pipeline is mostly dry.
A major reason for poor efficacy of antifungal treatments is most fungal organisms grow as ‘biofilms’ on surfaces of implantable medical devices, and the biofilms are significantly less susceptible to antifungal drugs compared to free-floating or planktonic cells. Biofilm infections are notoriously difficult to treat, and they commonly manifest as chronic or recurrent infections, and constitute a number of clinical challenges.
Biofilms are complex three-dimensional structures, which are composed of different morphological forms of the organism including yeast, pseudohyphae and hyphae, in an extracellular matrix. The antifungal resistance of biofilms is primarily attributed to changes in genetic, physiological and molecular characteristics of the cells in the biofilm, and secondarily to slow diffusion of drugs, and the binding of drugs to the biofilm matrix. Thus, there is a need to develop new strategies for the screening and discovery of antifungal drugs that prevent or control the formation of biofilms. The current industry standard is 96-well plate assay, which, when invented in 2001 was revolutionary and it changed the way fungal biofilms were examined. Prior to 2001, growth and characterization of fungal biofilms was an ordeal, and was performed by only a handful of investigators by mostly forming one biofilm at a time. However, practical considerations of time, cost and reagent volume severely limit the use of 96-well plate assays for probing diverse set of chemical libraries containing tens of thousands of molecules for new drugs, and novel, innovative technologies are sorely needed.